*{
    margin: 0;
    padding: 0;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #222;
}
.box{
    position: relative;
    width: 300px;
    height: 300px;
    border-radius:50% ;
    box-shadow: inset 0 0 50px #000;
    background: #222;
    z-index: 1000;
}
.box .number{
    position: absolute;
    top:0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;

}
.box .number h2{
    color: #777;
    font-weight: 700;
    font-size: 40px;
    transition: 0.5s;
}
.box:hover .number h2{
    color: #fff;
    font-size: 50px;
}
svg{
    position: relative;
    width: 300px;
    height: 300px;
    z-index: 999;
    transform: rotate(-90deg);
}
#inner{
    stroke-dashoffset:1000;
    animation: offset 10s linear 0s 1;
    -webkit-animation:offset 10s linear 0s 1; /*Safari and Chrome*/
    animation-fill-mode:forwards;
    -webkit-animation-fill-mode:forwards; /* Safari 和 Chrome */
}
@keyframes offset{
    0%{
        stroke-dashoffset:1000;
    }
    100%{
        stroke-dashoffset:0;
    }
}